Turbine Overspeed Trip Test Data Logging System

ABSTRACT

A turbine overspeed trip test data logging system is a portable system by which an operator can electronically gather and log data for a turbine overspeed test. A plurality of sensors can be affixed to various components of the turbine for gathering test data to be received and compiled into a turbine test log by a processing unit. A method for processing the gathered sensor data is also provided.

The current application claims a priority to the U.S. Provisional Patentapplication Ser. No. 61/930,183 filed on Jan. 22, 2014.

FIELD OF THE INVENTION

The present invention relates generally to a data logging system. Morespecifically, the present invention is a system to allow routine testingand documentation of turbine overspeed trip systems that includesmeasurement and recording of all the system components: shaft speed, theactivation of the overspeed sensing device and the movement of the stopvalve or valves.

BACKGROUND OF THE INVENTION

Every steam or gas turbine installed in the world has a system toprotect it from a destructive overspeed event. If the turbine speedreaches a certain level, different for each machine depending on itsdesign, major mechanical failure will occur. Although there are manydifferent designs and configurations for the overspeed trip protectionsystem, every one of them is designed to sense when the shaft speedreaches a predetermined speed limit and then activate a shutdown system.

The simplest and most common protection systems consist of a mechanicaldevice mounted on the shaft that moves when the speed limit is reached.The mechanical device then strikes a stationary mechanism that is linkedto a valve. The interaction of the overspeed device and the mechanicallinkage results in the rapid closing of a steam or gas valve.

Systems can range from the simplest mechanical designs, as describedabove, to very sophisticated electronic detection and valve actuationsystems with very rapid response times. Whether simple or complex,however, the systems need to be tested from time to time to verifyproper operation.

In addition to simply verifying that the system functions, it is alsoimportant to measure the response of the system and document all of theresults. When a machine is equipped with an electronic control systemand that control system is integrated into an overall computerized plantcontrol system (DCS) then it is possible to perform an overspeed testand have the speed history during the test documented. However, the DCSonly stores speed versus time and does not measure or record anythingelse.

There is no system known to this writer which is designed to allow theoperator to measure anything more than speed when they are testing aturbine trip system. The “state of the art” for conducting overspeedtrip system tests is to visually monitor speed and either watch orlisten for the sudden closing of the stop valve. The operator mustvisually and mentally associate a speed value with the moment the tripsystem activates. This is true even for a system that records speed asdescribed above.

It is therefore an object of the present invention to allow routinetesting and documentation of turbine overspeed trip systems thatincludes measurement and recording of all the system components: shaftspeed, the activation of the overspeed sensing device and the movementof the stop valve or valves.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the present invention in use with aturbine with a mechanical overspeed detection system.

FIG. 2 is a block diagram of the electrical components of the presentinvention and various possible sensor types to be used.

FIG. 3 is a stepwise flow diagram describing the general process ofusing the present invention.

FIG. 4 is a stepwise flow diagram describing the process for processingand displaying speed per time sensor inputs.

FIG. 5 is a stepwise flow diagram describing the process for processingand displaying an overspeed trip indication.

FIG. 6 is a stepwise flow diagram describing the process for processingand displaying a valve closing signal.

FIG. 7 is a stepwise flow diagram describing the process for processingand displaying a maximum speed for the overspeed test.

FIG. 8 is a stepwise flow diagram describing the process for processingand displaying several time intervals for the overspeed test.

DETAIL DESCRIPTIONS OF THE INVENTION

All illustrations of the drawings are for the purpose of describingselected versions of the present invention and are not intended to limitthe scope of the present invention. The present invention is to bedescribed in detail and is provided in a manner that establishes athorough understanding of the present invention. There may be aspects ofthe present invention that may be practiced without the implementationof some features as they are described. It should be understood thatsome details have not been described in detail in order to notunnecessarily obscure focus of the invention.

The purpose of the proposed system is to allow routine testing anddocumentation of turbine overspeed trip systems, including measurementand recording of all the system components: shaft speed, the activationof the overspeed detection system 6 and the movement of the stop valve 7or valves. The system will primarily be targeted at the market utilizingsimple steam turbines with purely mechanical trip systems and no meansof recording speed. It can be adapted, using different sensors, to aturbine with electronic controls so that the existing electronic datacan be incorporated into the test system data. The preferred embodimentof the present invention is as a portable kit which can be transportedto any given turbine installation location for use. The presentinvention utilizes a number of sensors, a data processing unit 2, andsoftware for recording and processing data from the sensors in order tocreate digital logs and documentation for turbine overspeed tests.

In the preferred embodiment, the present invention comprises a pluralityof sensors 1, a processing unit 2, and a data storage unit 3. Theapparatus of the present invention may be transported in a hardshellenclosure for convenience. In the preferred embodiment, the plurality ofsensors 1 comprises a rotational speed sensor 11, an overspeed tripdetection sensor 12, and a stop valve actuation sensor 13. Therotational speed sensor 11 measures the rotational speed of a shaft 4 ofthe turbine to be tested. The overspeed trip detection sensor 12 detectsan overspeed condition trip of the turbine, which is caused by anoverspeed detection system 6 of the turbine. That is, upon detection ofan overspeed condition, the overspeed detection system 6 causes anoverspeed condition trip in order to shut down the turbine. The stopvalve actuation sensor 13 detects movement of a stop valve 7, whichplugs a steam line in order to cut off input to the turbine. Themovement of the stop valve 7 is triggered by the overspeed conditiontrip. The plurality of sensors 1 and the data storage unit 3 areelectronically connected to the processing unit 2.

It is common for overspeed detection systems to utilize a mechanicalmeans to detect an overspeed condition. In this case, a hollow shaftoriented laterally to the axis of the turbine shaft 4 within the turbineshaft 4 contains a pin affixed to a spring. As the turbine shaft 4 spinsfaster, the pin experiences centrifugal inertia of motion, causing thepin to move further toward the exterior of the turbine shaft 4. At acertain threshold speed calibrated by the tension of the spring, the pinprotrudes from the body of the turbine shaft 4 and strikes a triplinkage, which in turn causes the stop valve 7 to close and prevent anyfurther steam from entering the turbine, effectively shutting theturbine down. While this is one way an overspeed detection system 6 canfunction, there are many other means for accomplishing the same goal. Inthis case, the pin striking the trip linkage or trip linkage strikerfunctions as an overspeed trip actuation device 6. In other systems,other overspeed trip actuation device 6s or means may be used, to whichthe present invention may be adapted accordingly.

To utilize the present invention to perform a turbine overspeed test,each of the plurality of sensors 1 is affixed to one of variouscomponents of the turbine and the overspeed detection system 6 of theturbine. In the preferred embodiment of the present invention, therotational speed sensor 11 is affixed directly to the turbine shaft 4.In this embodiment, the rotational speed sensor 11 comprises a strip ofreflective tape and a laser probe. The strip of reflective tape isaffixed to the turbine shaft 4, and the strip of reflective tape is readby the laser probe as the turbine rotates in order to measure therotational speed of the turbine shaft 4. In another embodiment, therotational speed sensor 11 is a tachometer that is pre-installed andalready comprised by the turbine. The processing unit 2 may connect tothe tachometer in order to receive data input from the tachometer. Inthis case, the present invention must additionally comprise anappropriate connection means such as a connector cable or wirelesscommunication device in order to interface with the computer systemassociated with the turbine or with the tachometer itself. Other typesof rotational speed sensors may be used as useful or appropriate,including, but not limited to, magnetic rotational speed sensor,electrical rotational speed sensors, frictional rotational speedsensors, or other rotational speed sensors.

In the preferred embodiment, the overspeed trip detection sensor 12 isremovably affixed to the overspeed trip actuation device 6 of theoverspeed detection system 6. Alternatively, the overspeed tripdetection sensor 12 is removably affixed near the overspeed tripactuation device 6 or to a secondary linkage or device actuated by theoverspeed trip actuation device 6, if that is sufficient to acquiresensor readings or required depending on the construction of theoverspeed detection system 6. In the preferred embodiment of the presentinvention, the overspeed trip detection sensor 12 is a piezoelectricsensor. The overspeed trip detection sensor 12 may be a sound sensor ora movement sensor as appropriate for the application. The overspeed tripdetection sensor 12 is not limited to being a piezoelectric sensor,however. Detection of the overspeed condition trip may conceivably bedone in a variety of ways, and thus the overspeed trip detector maybelong to one of a number of sensor types, including, but not limitedto: voltage measurement of the current through an electrical solenoidvalve, inertia switches, magnetic sensors, friction sensors, or opticalsensors.

The stop valve actuation sensor 13 is removably affixed to the stopvalve 7 of the overspeed detection system 6. Similar to the overspeedtrip detection sensor 12, the stop valve actuation sensor 13 may beremovably affixed near the stop valve 7 or to a linkage connected to thestop valve 7 as appropriate, useful or necessary depending on the designof the turbine and/or the overspeed detection system 6. In the preferredembodiment, the stop valve actuation sensor 13 is a movement sensor thatdetects either when the stop valve 7 begins moving, ends moving, orboth. However, similar to the overspeed trip detection sensor 12, thestop valve actuation sensor 13 may belong to any class or type of sensorthat facilitates detection of the stop valve 7 closing.

The plurality of sensors 1 of the present invention is not limited tothe rotational speed sensor 11, the overspeed trip detection sensor 12and the stop valve actuation sensor 13. Potentially, any other sensorswhich can provide valuable data for a turbine overspeed test may beadditionally comprised by the plurality of sensors 1. One suchadditional sensor is a pressure sensor. The purpose of the pressuresensor is to monitor the pressure or steam input to the turbine, whichis another variable which can be valuable for operational testing of aturbine. The pressure sensor may either be removably placed within asteam line of the turbine, or the pressure sensor may be a pre-installedcomponent with which the present invention may interface, similar to thetachometer. Additionally, the plurality of sensors 1 may also comprise avibration sensor which is removably attached to the turbine. Thevibration sensor may be any useful sensor for detecting vibration of theturbine shaft 4 such as, but not limited to, an accelerometer, a soundvibration sensor, or another type of vibration sensor. Vibration of theturbine shaft 4 is desirable to measure in order to ascertain whetherthe turbine shaft 4 has any rotational imbalances which could lead toundesirable wear or damage to the turbine.

It should be noted that more than one individual sensor and/or sensormeans may be utilized for each of the rotational speed sensor 11, theoverspeed trip detection sensor 12, the stop valve actuation sensor 13,or any additional sensors for measuring various other relevant variable,and each of said sensor is not necessarily limited to a single sensor orsensor type.

In addition to the physical apparatus, the present invention includes amethod for utilizing the turbine overspeed trip test data loggingsystem. The method is preferably a software program or multiple softwareprograms which function together or in separate steps in order toadequately collect and process data from the plurality of sensors 1 andto compile a report for evaluation and documentation purposes.

In the method of the present invention, a storage media and theplurality of sensors 1 are provided, in addition to a plurality ofturbine test parameters. The plurality of turbine test parameterscomprises, but is not limited to, a normal operating speed, a designatedoverspeed trip speed, a maximum allowable speed, a test date, a testoperator identification, and a turbine identification. The designatedoverspeed trip speed is the speed at which the overspeed detectionsystem 6 is designed to recognize an overspeed condition of the turbine.Each of the plurality of turbine test parameters are predefined andinput into the software for each turbine overspeed test as part of aturbine test log.

A plurality of test readings are continually received from the pluralityof sensors 1 during a test time interval, with each of the test readingsbeing associated with a time stamp. The time at which any given sensorreading is taken should be able to be identified for evaluation andlogging purposes. A plurality of test metrics are calculated from thetest readings. Subsequently, the turbine test parameters, the testreadings, and the test metrics are compiled into a turbine test log, andthe turbine test log is stored in the storage media.

In order to review the turbine test log, a digital display is provided.The processing unit 2 and/or storage media, whatever form they take, iselectronically connected to the digital display. Each of the testmetrics is displayed on the digital display alongside any appropriatelabeling for documentation purposes.

One of the test metrics is a speed per time graph. The speed per timegraph is generated from the test reading from the rotational speedsensor 11, and the speed per time graph is displayed on the digitaldisplay. Another test metric is an overspeed trip indication. The timestamp of the overspeed trip indication is designated as an overspeedtrip time stamp if the overspeed trip indication is received as one ofthe test readings from the overspeed trip detection sensor 12. Uponviewing the turbine test log, the overspeed trip time stamp is displayedon the digital display. Another test metric is a valve closing timestamp. If a valve closing signal is received as one of the test readingsfrom the stop valve actuation sensor 13, the time stamp of the valveclosing signal is designated as a valve closing time stamp. The valveclosing time stamp is subsequently displayed on the digital display aspart of the turbine test log.

Another of the test metrics is a maximum speed. A plurality of speedreadings is received as test readings from the rotational speed sensor11 over the test time interval, wherein each of the plurality of speedreadings is a rotational speed of the turbine shaft 4 at an associatedpoint in time. The maximum speed is calculated from the plurality ofspeed readings, and the time stamp of the speed reading of the maximumspeed is designated as the maximum speed time stamp. The maximum speedmay be calculated from the plurality of speed readings by any usefulalgorithm for finding the maximum value from a plurality of values.

It is also desirable to calculate several other time intervals for theturbine test log. Such time intervals include, but are not limited to,the time between the overspeed trip and the stop valve 7 closing, thetime between the stop valve 7 closing and the maximum speed, and thetime between the overspeed trip and the maximum speed. To this end, afirst time difference is calculated between the overspeed trip timestamp and the valve closing time stamp. Similarly, a second timedifference is calculated between the valve closing time stamp and themaximum speed time stamp, and a third time difference is calculatedbetween the overspeed trip time stamp and the maximum speed time stamp.The first time difference, the second time difference, and the thirdtime difference are displayed on the digital display as part of theturbine test log along with appropriate labeling. Another desirable timeinterval to calculate may include but is not limited to a timedifference between when the stop valve 7 begins to close and when thestop valve 7 finishes closing, in order to more precisely evaluate theoverspeed trip detection system.

Although the invention has been explained in relation to its preferredembodiment, it is to be understood that many other possiblemodifications and variations can be made without departing from thespirit and scope of the invention as hereinafter claimed.

What is claimed is:
 1. A turbine overspeed trip test data logging system comprises: a plurality of sensors; a processing unit; a data storage unit; the plurality of sensors comprises a rotational speed sensor, an overspeed trip detection sensor and a stop valve actuation sensor, wherein the rotational speed sensor measures the rotational speed of a shaft of a turbine; wherein the overspeed trip detection sensor detects an overspeed condition trip of the turbine by an overspeed detection system of the turbine; wherein the stop valve actuation sensor detects movement of a stop valve of the overspeed detection system triggered by the overspeed condition trip; and the plurality of sensors and the data storage unit being electronically connected to the processing unit.
 2. The turbine overspeed trip test data logging system as claimed in claim 1 comprises: the rotational speed sensor being removably affixed to the turbine shaft.
 3. The turbine overspeed trip test data logging system as claimed in claim 2 comprises: the rotational speed sensor comprises a strip of reflective tape and a laser probe, wherein the strip of reflective tape is affixed to the turbine shaft and wherein the strip of reflective tape is read by the laser probe in order to measure the rotational speed of the turbine shaft.
 4. The turbine overspeed trip test data logging system as claimed in claim 1 comprises: the rotational speed sensor being a tachometer comprised by the turbine, wherein the processing unit may receive data input from the tachometer.
 5. The turbine overspeed trip test data logging system as claimed in claim 1 comprises: the overspeed trip detection sensor being removably affixed to an overspeed trip actuation device of the overspeed detection system.
 6. The turbine overspeed trip test data logging system as claimed in claim 1 comprises: the stop valve actuation sensor being removably affixed to a stop valve of the overspeed detection system.
 7. The turbine overspeed trip test data logging system as claimed in claim 1 comprises: the overspeed trip detection sensor being a piezoelectric sensor, wherein the piezoelectric sensor is attached to an overspeed trip actuation device;
 8. The turbine overspeed trip test data logging system as claimed in claim 7 comprises: the piezoelectric sensor being a sound sensor.
 9. The turbine overspeed trip test data logging system as claimed in claim 1 comprises: the overspeed trip detection sensor being a movement sensor.
 10. The turbine overspeed trip test data logging system as claimed in claim 1 comprises: the stop valve actuation sensor being a movement sensor.
 11. The turbine overspeed trip test data logging system as claimed in claim 1 comprises: the plurality of sensors further comprises a pressure sensor, wherein the pressure sensor is removably positioned within a steam line of the turbine.
 12. The turbine overspeed trip test data logging system as claimed in claim 1 comprises: the plurality of sensors further comprises a vibration sensor, wherein the vibration sensor is removably attached to the turbine.
 13. A method of using a turbine overspeed trip test data logging system by executing computer-executable instructions stored on a non-transitory computer-readable medium comprises the steps of: providing a storage media; providing a plurality of sensors comprising a rotational speed sensor, an overspeed trip detection sensor and a stop valve actuation sensor; providing a plurality of turbine test parameters, wherein the plurality of turbine test parameters comprises a normal operating speed, a designated overspeed trip speed, a maximum allowable speed, a test date, a test operator identification, and a turbine identification; continually receiving test readings from the plurality of sensors during a test time interval, wherein each of the test readings is associated with a time stamp; calculating a plurality of test metrics from the test readings; compiling the turbine test parameters, the test readings, and the test metrics into a turbine test log; and storing the turbine test log in the storage media.
 14. A method of using a turbine overspeed trip test data logging system by executing computer-executable instructions stored on a non-transitory computer-readable medium as claimed in claim 13 comprises the steps of: providing a digital display; generating a speed per time graph from the test readings from the rotational speed sensor; and displaying the speed per time graph on the digital display.
 15. A method of using a turbine overspeed trip test data logging system by executing computer-executable instructions stored on a non-transitory computer-readable medium as claimed in claim 13 comprises the steps of: providing a digital display; designating the time stamp of an overspeed trip indication as an overspeed trip time stamp, if the overspeed trip indication is received as one of the test readings from the overspeed trip detection sensor; and displaying the overspeed trip time stamp on the digital display.
 16. A method of using a turbine overspeed trip test data logging system by executing computer-executable instructions stored on a non-transitory computer-readable medium as claimed in claim 13 comprises the steps of: providing a digital display; designating the time stamp of a valve closing signal as a valve closing time stamp, if the valve closing signal is received as one of the test readings from the stop valve actuation sensor; and displaying the valve closing time stamp on the digital display.
 17. A method of using a turbine overspeed trip test data logging system by executing computer-executable instructions stored on a non-transitory computer-readable medium as claimed in claim 13 comprises the steps of: providing a digital display; receiving a plurality of speed readings as test readings from the rotational speed sensor over the test time interval; calculating a maximum speed from the plurality of speed readings; designating the time stamp of the speed reading of the maximum speed as a maximum speed time stamp; and displaying the maximum speed time stamp on the digital display.
 18. A method of using a turbine overspeed trip test data logging system by executing computer-executable instructions stored on a non-transitory computer-readable medium as claimed in claim 13 comprises the steps of: providing a digital display; receiving an overspeed trip indication as one of the test readings from the overspeed trip detection sensor; designating the time stamp of the overspeed trip indication as an overspeed trip time stamp; receiving a valve closing signal is as one of the test readings from the stop valve actuation sensor; designating the time stamp of the valve closing signal as a valve closing time stamp; receiving a plurality of speed readings as test readings from the rotational speed sensor; calculating a maximum speed from the plurality of speed readings; designating the time stamp of the speed reading of the maximum speed as the maximum speed time stamp; calculating a first time difference between the overspeed trip time stamp and the valve closing time stamp; calculating a second time difference between the valve closing time stamp and the maximum speed time stamp; calculating a third time difference between the overspeed trip time stamp and the maximum speed time stamp; and displaying the first time difference, the second time difference, and the third time difference on the digital display. 